• Title, Summary, Keyword: modification factor

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Evaluation of performance and seismic parameters of eccentrically braced frames equipped with dual vertical links

  • Mohsenian, Vahid;Nikkhoo, Ali
    • Structural Engineering and Mechanics
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    • v.69 no.6
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    • pp.591-605
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    • 2019
  • Investigations on seismic performance of eccentrically braced frames equipped with dual vertical links have received little attention. Therefore, the main goal of this paper is to describe design steps for such frames and evaluate nonlinear performance of this system according to the reliability analysis. In this study, four and eight story frame structures are analyzed and the response modification factors for different intensity and damage levels are derived in a matrix form based on a new approach. According to the obtained results, the system has high ductility and acceptable seismic performance. Moreover, it is concluded that using response modification factor equal to 8 in the design of system provides desirable seismic reliability under the design and maximum probable hazard levels. Due to desirable performance and significant advantages of the dual vertical links, this system can be used as a main lateral load bearing system, in addition to its application for rehabilitation of damaged structures.

An Improved Method for the Evaluation of Load Carrying Capacity of Existing Bridges (교량 구조물의 개선된 내하력 평가기법)

  • Oh, Byung-Whan;Kim, Ki-Su;Shin, Ho-Song;Lee, Woong-Jong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.1 no.1
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    • pp.53-64
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    • 1997
  • Recently, safety evaluation of structures has received great concern in this country. One major problem in safety evaluation is that the results are often quite different depending upon evaluation authority. This is mainly due to arbitrary selection of various modification factors when employing allowable stress method for safety evaluation, The purpose of the present study is, therefore, to establish a rational method to determine the modification factors, especially the stress modification factor and the deterioration modification factor based on visual examination. It is thought that the proposed method yields a rational and consistent result for safety evaluation and may efficiently be used for realistic evaluation of load capacity of bridge structures.

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Cross-cultural Validation of Instruments Measuring Health Beliefs about Colorectal Cancer Screening among Korean Americans

  • Lee, Shin-Young;Lee, Eunice E.
    • Journal of Korean Academy of Nursing
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    • v.45 no.1
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    • pp.129-138
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    • 2015
  • Purpose: The purpose of this study was to report the instrument modification and validation processes to make existing health belief model scales culturally appropriate for Korean Americans (KAs) regarding colorectal cancer (CRC) screening utilization. Methods: Instrument translation, individual interviews using cognitive interviewing, and expert reviews were conducted during the instrument modification phase, and a pilot test and a cross-sectional survey were conducted during the instrument validation phase. Data analyses of the cross-sectional survey included internal consistency and construct validity using exploratory and confirmatory factor analysis. Results: The main issues identified during the instrument modification phase were (a) cultural and linguistic translation issues and (b) newly developed items reflecting Korean cultural barriers. Cross-sectional survey analyses during the instrument validation phase revealed that all scales demonstrate good internal consistency reliability (Cronbach's alpha=.72~.88). Exploratory factor analysis showed that susceptibility and severity loaded on the same factor, which may indicate a threat variable. Items with low factor loadings in the confirmatory factor analysis may relate to (a) lack of knowledge about fecal occult blood testing and (b) multiple dimensions of the subscales. Conclusion: Methodological, sequential processes of instrument modification and validation, including translation, individual interviews, expert reviews, pilot testing and a cross-sectional survey, were provided in this study. The findings indicate that existing instruments need to be examined for CRC screening research involving KAs.

Estimation of Response Modification Factor and Nonlinear Displacement for Moment Resisting Reinforced Concrete Frames (철근콘크리트 연성 모멘트골조에 대한 반응수정계수와 비선형 변위량의 평가)

  • 김길환;전대한;이상호
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.2
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    • pp.29-37
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    • 2002
  • The purpose of this study is to provide a fundamental data of earthquake resistant design through the estimation of the response modification factor and nonlinear displacement for moment resisting reinforced concrete frames by linear and nonlinear static analysis. The analysis models are designed in accordance with AIK code and then, estimated the response modification factor and nonlinear displacement of the buildings. The parameters such as story numbers(10, 20, 30), plan ratios(1:1, 1:2) and analysis types(2D, 3D) of building structure are chosen for use in this study. After comparing the results of linear and nonlinear static analysis, the response modification factor is obtained as the product of four factors: ductility factor, strength factor, damping factor and redundancy factor. The response modification factor are close to 3.5 in case of 2 span, 4.3 in case of 3 span and 5.0 in case 4 or more span models regardless number of stories and plan ratios. The nonlinear displacement is evaluated from the ratio of story drift angle(nonlinear drift/linear drift). The ratio of story drift angle increases as story numbers increase and the value varies from 5.85 to 9.34.

Evaluation of Response Modification Factor of Steel Special Resisting Frame Building Before and After Retrofitted with Buckling Restrained Brace (비좌굴가새의 보강 전과 후의 철골 특수모멘트저항골조 건물의 R계수 평가)

  • Shin, Jiuk;Lee, Kihak;Jo, Yeong Wook
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.1
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    • pp.11-19
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    • 2013
  • This research presents that seismic performance of steel moment resisting frame building designed by past provision(UBC, Uniform Building Code) before and after retrofitted with BRB (Buckling-Restrained Brace) was evaluated using response modification factor (R-factor). In addition, the seismic performance of the retrofitted past building was compared with that specified in current provision. The past building considered two different connections: bilinear connection, which was used by structural engineer for building design, and brittle connection observed in past earthquakes. The nonlinear pushover analysis and time history analysis were performed for the analytical models considered in this study. The R-factor was calculated based on the analytical results. When comparing the R-factor of the current provision with the calculated R-factor, the results were different due to the hysteresis characteristics of the connection types. After retrofitted with BRBs, the past buildings with the bilinear connection were satisfied with the seismic performance of the current provision. However, the past buildings with the brittle connection was significantly different with the R-factor of the current provision.

Response modification factor and seismic fragility assessment of skewed multi-span continuous concrete girder bridges

  • Khorraminejad, Amir;Sedaghati, Parshan;Foliente, Greg
    • Earthquakes and Structures
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    • v.20 no.4
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    • pp.389-403
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    • 2021
  • Skewed bridges, being irregular structures with complicated dynamic behavior, are more susceptible to earthquake damage. Reliable seismic-resistant design of skewed bridges can be achieved by accurate determination of nonlinear seismic demands. However, the effect of geometric characteristics on the response modification factor (R-factor) is not accounted for in bridge design practices. This study attempts to investigate the effects of changes in the number of spans, skew angle and bearing stiffness on R-factor values and to assess the seismic fragility of skewed bridges. Results indicated that changes in the skew angle had no significant effect on R-factor values which were in consonance with code-prescribed R values. Also, unlike the increase in the number of spans that resulted in a decrease in the R-factor, the increase in bearing stiffness led to higher R-factor values. Findings of the fragility analysis implied that although the increase in the number of spans, as well as the increase in the skew angle, led to a higher failure probability, greater values of bearing stiffness reduced the collapse probability. For practicing design engineers, it is recommended that maximum demands on substructure elements to be calculated when the excitation angle is applied along the principal axes of skewed bridges.

Evaluation of Ductility Factors for MDOF Systems in Special Steel Moment Resisting Frames (철골 연성 모멘트 골조에 대한 다자유도 시스템의 연성계수 평가)

  • Kang, Cheol-Kyu;Han, Young-Cheol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6
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    • pp.13-22
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    • 2004
  • Ductiluty factor has played an important role in seismic design as it is key component of response modification factor(R). In this stuty, ductility factors() are calculated by multiplying ductility factor for SDOF systems() and MDOF modification factors(). Ductility factors() for SDOF systems are computed from nonlinear dynamic analysis undergoing different level of displacement ductiluty demands and period when subjected to a large number of recorded earthquake ground motions. The MDOF modification factors() are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames are designed to investigate the ductility factors considering the number of stories(4, 8 and 16-stories), framing system(Perimeter Frames, PF and Distributed Frames, DF), failure mechanism(Strong-Column Weak-Beam, SCWB and Weak-Column Strong-Beam, WCSB), soil profiles(SA, SC and SE in UBC 1997) and seismic zone factors(Z=0.075, 0.2 and 0.4 in UBC 1997). It is shown that the number of stories, failure mechanisms (SCWB, WCSB), and soil profiles have great influence on the ductility factors, however, the structural system(Perimeter frames, Distributed frames), and seismic zones have no influence on the ductility factors.

Oxidative Stress, Nrf2, and Epigenetic Modification Contribute to Anticancer Drug Resistance

  • Kang, Kyoung Ah;Hyun, Jin Won
    • Toxicological Research
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    • v.33 no.1
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    • pp.1-5
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    • 2017
  • Nuclear factor E2-related factor 2 (Nrf2), a transcription factor, controls the expression of genes encoding cytoprotective proteins, including antioxidant enzymes that combat oxidative and electrophilic stress to maintain redox homeostasis. However, recent studies demonstrated that, in cancer, aberrant activation of Nrf2 by epigenetic alterations promotes high expression of cytoprotective proteins, which can decrease the efficacy of anticancer drugs used for chemotherapy. In this review, we summarize recent findings regarding the relationship between oxidative stress, Nrf2, epigenetic modification, and anticancer drug resistance, which should aid in development of new strategies to improve chemotherapeutic efficacy.

An Evaluation Study On Response Modification Factor of Unreinforced Mansonry Structure (비보강 조적조 건축물의 반응수정계수 설정에 관한 연구)

  • Kwon, Ki-Hyuk;Lee, Yong-Hwan;Yi, Waon-Ho;Lee, Jung-Han;Kang, Dae-Eon
    • 한국방재학회:학술대회논문집
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    • pp.33-36
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    • 2007
  • This study shows the basic data for setting up a response modification factor of unreinforcement masonry structure by considering and analyzing the experiment results of the domestic walls. If the result of this study compare with the value R of KBC-2005, 1.5, the average value, 1.2, is the low value. However, the maximum value, 2.57, is more than 70% bigger than the standard value. The standard value of overstrength factor, 2.5 is judged to have relatively bigger value than this study.

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Over-Strength, Ductility and Response Modification Factor of Small-Size Reinforced Concrete Moment Frame Buildings (소규모 철근콘크리트 모멘트골조 건축물의 초과강도, 연성도 및 반응수정계수)

  • Kim, Taewan;Chu, Yurim;Park, Hong-Gun;Shin, Yeong Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.20 no.3
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    • pp.145-153
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    • 2016
  • Small-size buildings are not designed by professional structural engineers in Korea. Therefore, their seismic performance can not be exactly estimated because their member sizes and reinforcement may be over- or under-designed. A prescriptive design criteria for the small-size buildings exists, but it also provides over-designed structural members since structural analysis is not incorporated, so it is necessary to revise the prescriptive criteria. The goal of this study was to provide an information for the revision, which is seismic performance and capability of small-size reinforced concrete moment frame buildings. For the study, the state of existing small-size reinforce-concrete buildings such as member size and reinforcement was identified by investigating their structural drawings. Then, over-strength, ductility and response modification factor of the small-size reinforced concrete moment frame buildings were estimated by analytical approach along with seismic performance check. The result showed that they possess moderate over-strength and ductility, and may use slightly increased response modification factor.